Fixed numerous bitfield problems.

Fixed numerous bitfield problems.

* src/SDCC.y: More bitfield related error checking
* src/SDCCsymt.h,
* src/SDCCsymt.c (compStructSize): fixed bitfield offset calc
* support/Util/SDCCerr.h,
* support/Util/SDCCerr.c: Added & edited some bitfield err msgs
* src/mcs51/gen.c (genPackBits, genUnpackBits): fixed mask bugs
* src/ds390/gen.c (genPackBits, genUnpackBits): fixed mask bugs
* support/regression/tests/bitfields.c: tests added

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@2826 4a8a32a2-be11-0410-ad9d-d568d2c75423